Mounting arm of a lighting fixture



FIG. 1 is a top perspective view.

FIG. 2 is a right side elevation view, the left side being a mirror image.

FIG. 3 is a top plan view; and,

FIG. 4 is a bottom plan view.

The broken lines are provided for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a mounting arm of a lighting fixture, as shown and described. 